Variations in the Mineral Composition of Herbarium Plant Species Collected During the Last Three Centuries

Mineral content (dry weight basis) was determined for herbarium specimens of 12 C3 plants (trees, shrubs and herbs) collected during the last 250 years in N.E. Spain. Present values of Al, Ca, Cu, Sr, Fe, P, Mg, Mn, K, Na, S, and Zn were always lower than in any other period of the last three centuries. Only one C4 plant was analysed. It presented a similar pattern to the C3 plants. These results are in accordance with experimental results that have shown that the mineral content of plants grown in elevated CO2 is generally lowered. Increased atmospheric CO2 and other anthropogenic environmental changes are suggested as possible causes of the changes in mineral content.